1, graphics card problems resulting in a computer black screen, as well as the monitor is bad.
2, the memory of the loose and motherboard memory slots poor contact or memory slots and memory damage.
3, the power supply does not work or damaged.
4, the line connection is bad (especially the bottom plate to the motherboard power supply 5PIN or 6PIN line).
5, the motherboard static electricity does not work (may be with your dust resulting in poor contact between the motherboard and the motherboard and static electricity causes).
According to the description of the questioner, in the case of ensuring that the main power supply has power, you can rule out the following aspects of the solution:
1, to confirm that the back of the industrial computer power supply is on the main switch.
2, industrial computer power supply inside a small green light is bright, not bright, if you use a metal wire to the power supply plug in the bottom of the plug on the fourth pin of the fifth pin shorting (a black a green line). If the power supply fan turns, prove that there is no problem with the power supply, the power supply does not turn to prove that the power supply has a problem. (If you don't know, change a power supply to try)
3, re-unplugging the motherboard, with a rubber inserted into the motherboard metal finger insertion and then installed inside the slot.
4, clear down the CMOS, the easiest way is that you do not have power in the case of the computer to pull down the motherboard button battery, wait about three minutes and then press up.
The above methods gradually try.
You can message me if you have any questions, and I can answer them in detail!